Graft copolymer additives for vinyl chloride polymer compositions

ABSTRACT

Novel additives comprising graft copolymers of a methyl methacrylate polymer onto copolymers of lower alkyl acrylates with either benzyl acrylate or vinylidene chloride are disclosed. It is further shown that these additives provide excellent results in the preparation of clear, impact resistant, thermoplastic compositions which comprise blends of the aforedescribed additives with a homo- or copolymer of vinyl chloride.

United States Patent [191 7 Protzman 260/885 Gallagher June 28, 1974 [5 GRAFT COPOLYMER ADDITIVES FOR 3,041,309 6/1962 Baer 260/876 R VINYL CHLORIDE POLYMER 3,475,516 10/1969 Bauer et al 260/876 R COMPOSITIONS [75] Inventor: Ruth Gallagher, Dobbs Ferry, NY. P i E i -M rr y Till a [73] Assignee: Stauffer Chemical Company, New Ass'stam Exammer c' Seccuro York, NY.

[22] Filed: Aug. 19, 1971 e 211 Appl. No.1 165,804 [571 ABSTRAQT Related Application Dam Novel additives comprising graft copolymers of a [62] Division of Scr. No. 28,897. methyl methacrylate polymer onto copolymers of i lower alkyl acrylates with either benzyl acrylate or vi- [52] US. Cl. 260/885, 260/23.5 R, 260/30.6 R, nylidene chloride are disclosed. It is further shown 260/31.8 M, 260/45.75 K, 260/876 R, that these additives provide excellent results in the 260/881, 260/884 preparation of clear, impact resistant, thermoplastic [58] a Field of Search 260/884, 885 compositions which comprise blends of the aforedescribed additives with a homoor copolymer of vinyl [56] References Cited chloride. UNITED STATES PATENTS 1 2,992,203 7/1961 9 Claims, 2 Drawing Figures REFRACTIVE INDEX (AT 23C.)

IENIEmuuzs m4 sum 1 or 2 BY WT., VINYLIDENE CHLORIDE I I00 80 6O 4O 2O BY WT. QBUTYL ACRYLATE REFACTIVE INDEX VS COPOLYMER COMPOSITION F|G.l

A. POLYBUTYL ACRYLATE B. POLYMETHYL METHACRYLATE C. POLY-VINYL CHLORIDE D.(54= 39 =7) POLY(METHYL METHACRYLATE STYRENE= ACRYLONITRILE) E. (75= 25) POLY(STYRENE=ACRYLONITRILE) F. PO LYVINYLI DENE CHLORIDE PATENTEDJIIIIZB I874 SHEEI 2 BF 2 B Y WT., BENZYL ACRYLATE INDEX REFRACTIVE (AT 23C.)

% BY WT., BUTYL ACRLATE REFRACTIVE INDEX VS COPOLYMER COMPOSITION F I G. 2

A. POLYBUTYL ACRY LATE B. POLYMETHYL METHACRYLATE C. POLY VINYL CHLORIDE D.(54=39=7) POLYIMETHYL METHACRYLATE=STYRENE= ACRYLONITRILE) E. POLYBEN ZYL ACRYLATE 1' GRAFT COPOLYMER ADDITIVES FOR VINYL CHLORIDE POLYMER COMPOSITIONS RELATED APPLICATION This application is a division of application Ser. No. 28,897, filed Apr. 15, 1970, now abondoned.

BACKGROUND OF THE INVENTION polystyrene, styrene-acrylonitrile copolymers and the like. As is known to those skilled in the art, the possession of a high degree of impact strength, i.e., the ability to withstand a rapidly applied shock, is" an extremely desirable characteristic in any thermoplastic which is to be used for the preparation of cast or molded objects.

With respect to PVC and the rigid copolymers of vinyl chloride, the rubber additives most commonly utilized for the improvement of impact strength are the polyacrylates, polybutadiene and the copolymers of butadiene with acrylonitrile and/or styrene. Unfortunately, the use of the latter types of impact additives does not provide completely satisfactory results. Thus, while polybutadiene and the butadiene copolymers yield blends with PVC or with vinyl chloride copolymers which display good impact strength and clarity, such blends are generally characterized by the fact that they become yellow during subsequent processing steps and also by their poor, long term oxidative stability. On the other hand, the use of polyacrylate impact addi-' tives, yields compositions whichliave good stability but which are, however,-decidedly opaque.

It is, therefore, a prime object of this invention to provide a novel class of additives for use with ,the

homoand copolymers of vinyl chloride which, when blended with the, latter polymers, will yield compositions which while displaying high impact strength will also be characterized by their outstanding clarity, the absence of yellowing during processing and their-excellent long term oxidative stability. Various other objects and advantages of this invention will be apparent from the disclosure which follows hereinafter.

TECHNICAL DISCLOSURE OF THE INVENTION It has now been discovered that the use, as impact additives for PVC and the rigid copolymers of vinyl chloride, of copolymers of the C -C alkyl esters of acrylic acid with either benzyl acrylate or vinylidene chloride yields high impact compositions of excellent clarity which do not yellow during processing and which have good long term oxidative stability.

The novel impact additives of this invention comprise copolymers of:

1. One or more C -C alkyl' acrylates including, for example, methyl, butyl, isobuty, n-hexyl, 2-ethylhexyl, n-octyl, nonyl, decyl and lauryl acrylate with the use of butyl acrylate being preferred; and

' 2. a second monomer selected from the group consisting of benzyl acrylate and vinylidene chloride. Also applicable are substituted benzyl acrylates, i.e., wherein the phenyl ring of the benzyl acrylate may be substituted with one or more lower alkyl, halo or nitrile groups.

, 2 It should be noted at this point, that the term copolymer, as used in this disclosure, is meant to encompass polymers derived from mixtures of two, three, or four or more monomers.

While the copolymers of some of the C -C alkyl acrylates are disclosed in the literature, they have not heretofore been suggested for use as impact additives for PVC and the'rigid copolymers of vinyl chloride. However, the copolymers of the (l -C alkyl acrylates with benzyl acrylate are believed to comprise new compositions of matter which are not, per se, disclosed in the literature.

The polymeric substrates with which these novel impact additives may be blended as part of the novel process of this invention include, as already been stated, PVC and the rigid copolymers of vinyl chloride. The latter rigid copolymers include, for example, copolymers containing a major proportion, by weight, of vinyl chloride together with one or more ethylenically unsaturated comonomers which may include, for example: vinyl esters of aliphatic and aromatic acids such as vinyl v acetate, vinyl propionate and vinyl benzoate; vinylidene halides such as. vinylidene chloride; C C alkyl I esters of acrylic and methacrylic acid such as the methyl, butyl, 2-ethlhexyl and lauryl esters of acrylic and methacrylic acids; the C C monoand dialkyl esters of ethylenically unsaturated dicarboxylic acids such as dibutyl fumarate and mono-methyl maleate; ethylenically unsaturated aromatic compounds such as styrene and alpha-methyl styrene; ethylenically unsaturated monoand dicarboxylic acids, their amides, anhydrides, and nitriles such as acrylic, methacrylic, fu-

maric, maleic, itracon'ic, citraconic and aconitic acids; acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, maleimide and maleic anhydride; and, C C alkyl vinyl ethers such as methyl vinyl ether and stearyl vinyl ether. The preparation of PVC and of the rigid copolymers of vinyl chloride may be accomplished by means of polymerization procedures well known to those skilled in the art such, for example, as the free radical initiated bulk, suspensiomemulsion and solution polymerization techniques.

Particularly useful as a polymeric substrate for use in the process of this invention are copolymers of vinyl chloride with up to about, 20 percent, by weight, of vinyl acetate. It should also be noted that the impact additives of this invention can, if desired, be successfully employed with a variety of rigid thermoplastic polymers other than the homo-and copolymers of vinyl chloride. Thus, for example, these additives may be employed with polymethacrylonitrile, polymethyl methacrylate, polystyrene, poly( styrene-acrylonitrile),

poly(methyl' methacrylate-styrene-acrylonitrile), and poly (methyl methacrylate-ethyl acrylate) as well as any of the possible copolymers of acrylonitrile, methacrylonitrile, styrene, alpha-methyl styrene), methyl methacrylate and ethyl acrylate.

The preparation of the novel impact additives of this invention may be conveniently accomplished by means of emulsion polymerization procedures well known to those skilled in the art which may be of either the onestep or seeded type using conventional emulsifiers and water soluble, free radical initiating catalysts. Thus, the selected monomers may be emulsified in water containing an effective concentration, e. g., from about 0.05 to 5 percent, as based on the total weight of the monomer charge, of one or more anionic, nonionic or cationic 'ernulsifierssucmfor example, as the alkyl carboxylic acid salts,the alkyl sulfate salts, the alkyl sulfonate salts, the alkyl phosphate salts, the alkyl sulfosuccinate salts, the alkyl ar'yl ether alcohols and the alkyl aryl polyether-sulfate salts. As a water soluble catalyst, one may. utilizefrom about 0.05 to about l percent, as

based on the total weight of the monomer charge, of a peroxy type'compound such, for example, as hydrogen peroxide, ammonium, sodium or potassium persulfate latter range for a period of from about 0.25 to 20 hours.

The resulting copolymer emulsion should preferably have a resin solids content in the range of from about to 50 percent, by weight. The copolymer particles should have aparticle size in the range of from about 0.03 -I 2.0 micronswith the larger particle sizes being attained'by the use of seed polymerization procedures whereby the polymerization is'c'onducted in the presenceof a previously prepared emulsion containing particles of one of the above described copolymer addi tives. 1

The .novel impact additive copolymers of this invention should, be prepared so as to contain from about 5 to 99 percent, and preferably 30 to 70 percent, by weight, of one or more C .C alkyl acrylatesand from about 5 to 99 percent,and'preferably 30-70 percent,

by "weight,'of benzyl acrylate and/orvinylidene chloride. if desired, these polymeric impact additives may be prepared in crosslinked'form by the inclusion, in the initial polymerizationrecipe, of a vinyl monomercontaining at least two reactive vinyl groups such, for example, as butylene glycol dimethacrylate, ethylene glycol dimethacrylate, divinyl benzene, allyl methacrylate, allyl acrylate, divinyl oxyethyl ether and diallyl adipate.

The'moieties derived from these optional crosslinking.

monomers may be present in the impact additives of this inventionin a concentration of from about 0.1 to 5.0 percent, byweight.

; jOther optional monomers which are non-crosslinking I may also'be used in preparing the impact additive copolymers of this invention as a replacement for part of acrylic and methacrylic acid such as the methyl, butyl,

2-e'thylhexyl and lauryl esters of acrylic and methacrylic acid; the C,C, monoand dialkyl esters of ethylenically unsaturated dicarboxylic acids such as dibutylfurnarate, monomethyl maleate, ethylenically unsaturated aromatic compounds such as styrene and alphamethyl styrene; ethylenically unsaturated monoand dicarboxylic acids, theiramides. nitriles and anhydrides such as acrylic methacrylic, fuma'ric, maleic, itaconic, citraconic and aconitic acids, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, maleimide. and maleic anhydride; and, C -C alkyl vinyl .ethers such as methyl vinyl ether and stearyl vinyl ether.

. 4 The actual blending of the impact additives of this invention with the selected polymeric substrate, i;e., with PVC or with a rigid vinyl chloride copolymer, may be accomplished by means of any convenient procedure which will result in an intimate admixture of the'impact additive within the mass of the substrate polymer.

Thus, for example, the aqueous latex containing the particles of the copolymer additive may be coagulated or spray dried so as to yield the additive in a dry, powdery solid form which can then simply be mill blended or otherwise admixed with the substrate polymer which should also be in the form of a dry powder. Or, if desired, the additive and the substrate may be admixed while each is in the form of an aqueous latex or suspension and the resulting mixture coagulated or spray dried so asto obtain a dry blend.

. The blending operation may also be carried out by means of a procedurein which the PVCor vinyl chlorpolymerized'by means of an aqueous emulsion procedure, as described 'hereinabove, while in the presence of an aqueous emulsion containing particles of one or more of the copolymer additives of this invention. Alternatively, the PVC or rigid vinyl chloride copolym'er which comprises the substrate polymer can be poly-" merized by means of an aqueous suspension procedure, as will be described hereinbelow,.in the presence of an aqueous emulsion containing'one or more of the co polymer additives of this invention. With either of these blending procedures involving a polymerization step, the resulting impact resistant composition will be in the form of discrete particles of an interpolymer having an essentially heterogeneous composition in which the vinyl chloride homo or copolymer substrate. has been polymerized in and/or around the previously prepared impact additive copolymer, particles.

As is known to those skilled in the art, suspension polymerization involves a process wherein one or more monomers are dispersed in a suspension medium,usually water, which is a non-solvent forboththe monomer phase and the resulting polymer. The polymerization is then conducted, under agitation, in the presence of a suspending agent, such as talc, clay, polyvinyl, alcohol gelatine, hydroxymethyl cellulose or carboxymethyl cellulose, and a monomer soluble catalyst such as 'azobisisobutyronitrile, lauroyl peroxide, benzoyl peroxide, or isopropyl peroxydicarbonate. The resulting polymer particles are of a relatively larger mass, as

compared with the particles obtained from an emulsion polymerization procedure, and will tend to more rapidly separate out from the suspension.

With respect'to proportions, the novel, high clarity, impact resistant composition resulting from the process of this invention, i.e., the blends comprising an intimate admixture of the selected impact additive copolymer and a PVC or rigid vinyl chloride copolymer substrate,

should be prepared so that from about 1 to about 35 percent of their total weight may comprise one or more of the above described impact additive copolymers.

Optimum results are apparently realized with composi-' greater degree of impact resistance. It may also be noted that if the product resulting from the blending or interpolymerization of the impact additive copolymer with PVC, a rigid vinyl chloride copolymer or some other thermoplastic polymer substrate containing more of the impact additive copolymer than is required, the blend or interpolymer may be diluted with an additional quantity of the substrate polymer in order to achieve any desired level of impact resistance.

The selection of a particular impact additive copolymer for use in preparing a PVC or rigid vinyl'chloride copolymer blend will be governed by the refractive index of the PVC or rigid vinyl chloride copolymer sub strate with whichit is'to be admixed. Thus, the clarity, and therefore the utility, of the resulting blend is for the most part dependent upon choosing a copolymer additive whose refractive index (Rf) is essentially identical to the R, of thePVC or rigid vinyl chloride copolymer substrate which is to be admixed therewith. For example, since PVC, at about 20C., has a R, of from about 1.53-1.54, one could use, for example, a butyl acrylatewinylidene chloride (45:55) copolymer or a butyl acrylatezbenzyl acrylate (55:45) copolymer either of which has a R; of about 1.53. Or, one may employ any of the other copolymer additives of this invention which may have a R; value close to l .5 39 in order to obtain an impact resistant composition displaying a high degree of clarity. Therefore, as the difference between the R, value of the copolymer additive and the R, value of the PVC or of the vinyl chloride copolymer substrateis increased, the clarity of the resultingmixture will, in turn, be progressively decreased.

Accordingly, the practitioner in the art need merely determine the R, value of his polymeric substrate, using any of the commercially available refractometers, prior to selecting a particular copolymer additive for admixture therewith. Moreover,it is quite simple to prepare the copolymer additives of this invention so as to obtain products displaying a broad range of refractive indices. This is made possible by the fact that the R, of a particular copolymer system can be varied in a direct relationship to its monomer ratio.

for example, with respect to the copolymers of butyl acrylate and either benzyl acrylate or vinylidene chloride, an increase in either their benzyl acrylate or vinylidene chloride content results in an increase, in a direct linear relationship, in their R, value.

The above described relationship between the refractive indices of the copolymer additives of this invention and various polymeric substrates are demonstrated in the appended drawings. Thus,

FIG. 1 is a graph illustrating: (l) the R, values of various polymer substrates as depicted on the vertical axis; (2) the percent, by weight, of butyl'acrylate in a butyl acrylatezvinylidene' chloride copolymer system on the lower horizontal axis; and (3) the percent, by weight, of vinylidene chloride in the same copolymer system on the upper horizontal axis.

FIG. 2 on the other hand, is a graph illustrating: (l) the R, values of various polymer substrates on the vertical axis; (2) the percent, by weight, of butyl acrylate in a butyl acrylatezbenzyl acrylate copolymer system on the lower horizontal axis; and (3) the percent, by weight, of benzyl acrylate in this same copolymer system on the upper horizontal axis.

Thus, the diagonal line in each of FIGS. 1 and 2,

. readily reveals the relationship between the composi- FlG. 1 reveals that a butyl acrylatecopolymer containing about 50 percent, by weight, of vinylidene chloride will have a R, of about I53 and can, therefore, be used with PVC which has the identical R; value. On the other hand, FIG. 2 reveals that a copolymer of butyl acrylate with about 25 percent, by weight, of benzyl acrylate will have a R; of only about 1.49 and can be used with polymethyl methacrylate which has the identical R, value. In general, for use with a PVC or a rigid vinyl chloride copolmer substrate, the impact additive copolymers of this invention may have a monomer ratio in the range of from about 35:65 to 65:35 C -C alkyl acrylate esterzbenzyl acrylate or vinylidene chloride with one or more optional comonomers being able to replace a portion of the benzyl acrylate or vinylidene chloride content of the copolymer.

The high clarity, impact resistant compositions of this invention can be prepared so as to contain various optional additives which may include, for example, plasti cizers such as the alkyl esters of phthalic, adipic and sebacic acids and aryl phosphate esters such, for example, as dioctyl phthalate, ditridecyl phthalate and tricresyl phosphate, etc.; lubricants such as stearic acid or its metal salts, petroleum based waxes, mineral oils, polyethylene, etc.; and heat and light stabilizers such as Ca/Zn stearate, basic lead compounds,.tin compounds, epoxidized oils, phenyl salicylates, benzophenones and benzotriazoles, etc, For a more complete listing of plasticizers, lubricants, stabilizersand other functional additives, one may consult Polyvinyl Chloride by H. A. Sarvetnick published by Van Nostrand Reinhold Co., New York, N.Y., in 1969.

The high clarity, impact resistant polymeric compositions resulting from the admixture of one or more of the above described impact additive copolymers with PVC or a rigid vinyl chloride copolymer substrate may be utilized in any of the coating, impregnating and molding applications known to those skilled in the art. For example, these compositions may be used for preparing such diverse items as calendered films, blow molded bottles, extruded flat bed and blown films, extruded articles and tubing, etc. and in carrying out such processes as injection molding, fluidized bedcoating, electrostatic powder spraying and rotational coating, etc.

The following examples will further illustrate the embodiment of this invention. In these examples, all parts given are by weight unless otherwise noted.

EXAMPLE 1 This example illustrates the preparation of a number of butyl acrylatezvinylidene chloride copolymer rubber impact additives, for use in the process of this invention.

The following table describes the ingredients present in a number of polymerization recipes each of which was polymerized by being introduced into one quart bottles which were capped, and heated at C. for a period of 4 /2 hours while being rotated at 20 rpm. Recipes Nos. 8 and 9, however, were heated for 9 hours at 78C. while being rotated at rpm. The resulting copolymer products were obtained as stable aqueous latices having a resin solids content of about 27 percent, by weight, wherein the copolymer particles had a particle size range of from about 0.2-0.3 microns.

5 hours while being rotated at 37 rpm. In each case, there INITIAL COMPOSITION OF POLYMERIZATION RECIPE 2% EMULSIFIER AQUEOUS 7 "m BUTYLENE RECIPE COPOLYMER 1% AQUEOUS SOLUTION VINYLIDENE BUTYL GL Y COI.

NO. COMPOSITION H O SOLUTION OF K S,O,, CHLORIDE ACRYLATE STYRENE DIMETHACR YLATE I 68/30/2 315 90 45 54 I22 3.6 2 63/35/2 do. do. do. 63 I13 do. 3 53/45/2 do. do. do. 81 96 d 4 48/50/2 do. do. do. 90 87 do. 5 43/55/2 do. do. do. 99 77 do. 6 38/60/2 do. do. do. I08 68 do. 7 33/65/2 do. do. do. 117 59 do. 8 43/40/2/I5 do. do. do. 72 77 27 do. 9 48/40/2/10 do. do. do. 72 86 18 do l0 45/55 do. do. do. 99 80 (I) The monomer ratio of each copolymer in the Table is given in the sequence: butyl acryIate/vinylidene chIoride/butylene glycol dimethacrylate/styrene (styrene is present only in Nos. 8 & 9).

(2) An anionic surfactant comprising the bis(tridecyl) ester of sodium sulfosuccinic acid.

.WEX MP E This example illustrates the preparation of a number of impact resistant PVC compositions which contained,

respectively, the various copolymer additives whose preparation is described in Example I, hereinabove. In this instance, the procedure utilized for the prepartion of these compositions involved the polymerization of PVC in the presence of an aqueous latex of the previshown, the monomer ratio being directly determinative of the refractive index of the copolymer.

- was produced an aqueous suspension containing about 27 percent, by weight, of particles each of which comprised an intimate, essentially heterogeneous admixture of interpolymer of PVC and about 15 percent, as based on the total weight of each particle, of the particular copolymer additive in whose presence it had been polymerized. In these interpolymer particles, the vinyl chloride had been polymerized in and/or around the particles of the impact additive copolymer. These interpolymer particles were recovered from their respective suspensions on a Buchner funnel and then air dried. In this Table, the numbers assigned to the copolymer impact additives correspond to the number by which these additives were identified in the Table set forth in Example I hereinabove.

INITIAL COMPOSITION OF POLYMERIZATION RECIPE IMPACEADDITIVE IMPACT ADDITIVE I% SOLUTION 1 RECIPE COPOLYMER COPOLYMER OF METHYL AZOBISISO- VINYL LATEX NO. LfXTEX A ER CELLULOSE BUTYRONITRILE. CHLORIDE 150353 I l 56 I96 72 0.075 100 2 2 do, do. do do. d

3 3 d do. do do. do

4 4 d do. do do. do

5 5 do. (10. do do. do

6 6 do. do. do do. do

7 7 do. do. do do. do

8 8 do. do. do do. d

9 v 9 do, do. do do. do 10 I 0 do. do do do. do

The clarity of these interpolymer particles was evaluated by means of a procedure in which 3.0 parts of each respective interpolymer was mixed by hand for about 2-3 minutes with 6.5 parts of dioctyl phthalate and 0.1 parts of an alkyl tin thioglycollate stabilizer as sold by M & T Chemicals, Inc. under the trademark Thermolite 31. A thin layer of each of the resulting plastisol mixtures was then spread upon a petri dish. The thus coated dishes were thereupon heated in an oven set at 190C. for a period of about 25-30 minutes. Upon being removed from the oven, the dried plastisol coatings contained within each dish were visually examined in order to evaluate their clarity. The restuls of these observations are set forth in the following table:

1. The control comprised a sample of unmodified PVC which had been polymerized by means of the identical procedure described hereinabove with the exception that it was not conducted in the presence of an aqueous latex of an impact additive copolymer.

The results shown in the above Table indicate that maximum clarityis achieved, with PVC as the substrate, using butyl acrylatezvinylidene chloride copolymer additives which contain from about 55-60 percent, by weight, of vinylidene chloride. It is also revealed that styrene can be substituted for a portion of the vinylidene chloride content of the copolymer additive without any loss in clarity.

EXAMPLE Ill This example illustrates the preparation of a clear, impact resistant PVC composition by means of the process of this invention. Part 1 Preparation of a03 micron 55:4322 vinylidene chloride/Z-ethylhexyl acrylate/butylene glycol dimethacrylate Copolymer Latex.

The following reactants were introduced into a one quart bottle which was capped and heated for 3% hours at 70C. while being rotated at 20 rpm.

315 gms. H 0

68 ml of a 1 percent aqueous solution of the bis(- tridecyl) ester of sodium sulfosuccinic acid.

ml of a 2 percent aqueous solution of potassium persulfate.

99 gms. of vinylidene chloride 77 gms. '2-ethylhexyl acrylate 3.gms. butylene glycol dimethacrylate By means of this procedure a latex whose particles had a particle size of about 0.3 microns and which had a 25 percent resin solids content was obtained.

Part 2 Preparation of a 0.6 micron 55:43:2-vinylidene chloride/ethylhexyl acrylate/butylene glycol dimethacrylate Copolymer Latex.

The following reactants were introduced in a 1 quart bottle which was capped and heated for 3% hours at 7075C. while being rotated at 20 rpm.

73 gms. of the aqueous copolymer whose preparation was described in Part I hereinabove.

1.5 ml of a 1 percent aqueous solution of the bis (tridecyl) ester of sodium sulfosuccinic acid.

318 gms. water 39 ml. of 2 percent aqeuous solution of potassium persulfate.

88 gms. vinylidene chloride 69 gms. 2-ethylhexyl acrylate 3.6 gms. butylene glycol dimethacrylate This procedure yielded a latex whose copolymer particles had a particle size of about 0.6 microns and a, resin solids content of about 28 percent.

Part 3 Preparation of a PVC-(vinylidene chloridezZ- ethylhexyl acrylate: butylene glycol dimethacrylate) Suspension Emulsion lnterpolymer.

The following reactants were introduced into a one quart bottle which was capped and heated for 8 hours at 60C. while being rotated at 40 rpm.

54 gms. of the copolymer latex whose preparation was described in Part 2 hereinabove.

196 gms. water 72 ml. of a 1 percent aqueous solution of methyl cellulose.

0.075 gms. of azobisisobutyronitrile 100 gms. vinyl chloride This procedure yielded an aqueous solution suspension of particles each of which comprised an intimate, essentially heterogeneous admixture or interpolymer of PVC and about 15 percent, as based on the total weight of each interpolymer particle, of the impact additive copolymer whose preparation was described in Part 2 hereinabove. These interpolymer particles were recovered from the aqueous suspension on a Buchner funnel and then air dried.

EXAMPLE IV This example illustrates the results obtained upon evaluating the tensile and tensile impact strength of a number of the copolymer additives whose preparation was described in Example I as well as of the PVC additive interpolymer whose preparation was described in Part 3 of Example III. In each case, a comparison is provided in which the additive or interpolymer is diluted, i.e. physically admixed, with PVC.

In evaluating these additive copolymers and interpolymer products, they were either milled alone or first diluted with the indicated amount of a commercially available polyvinyl chloride resin. In either case, the milling was conducted on a two-roll mill operating at 350-360F. for a period of 3 minutes. As stabilizers, each sample contained 3 PHR of Thermolite 3 l and 0.5 PHR of calcium stearate. The following table describes the composition of the various samples which were evaluated as well as the results obtained.

FINAL CONCENTRATION PRODUCT 7r OF PVC" OF RUBBER TENSILE TENSILE APPEARANCE COPOLYMER BEING PRODUCT USED FOR ADDITIVE OR STRENGTH IMPACT STRENGTH OF MILLED TESTED USED DILUTION INTERPOLYMER (PSI) (F'I./LBS./IN) PRODUCT Unmodified PVC Control I 0 8,050 95 Clear Commercially Available Additive I0 90 6.800 H7 do. Copolymer No. of Example I I00 15 5,090 208 do. Copolymer No. 5 of Example I 66 33 10 6,230 I06 do. lnterpolymer of Example III, Part 3 I00 6,300 150 do. Interpolymer of Example III. Part 3 66 33 I0 6,900 133 do.

PVC having a relative viscosity of 2.l l as detennined at 30C. in a l gm/dcciliter solution of cyclohexanone.

" As determined by means of ASTM Procedure D-l708. As determined by means of ASTM Procedure D4822.

A methyl methacrylate: acrylonitrile: butadienezstyrene interpolymer sold as Kane Ace B-l2 by the Kanegafuchi Chemical Company.

The results shown in the above table indicate the improved impact strength inherent in the compositions resulting from the process of this invention when compared with unmodified PVC.

EXAMPLE V This example illustrates the preparation of a number of butyl acrylatezbenzyl acrylate copolymer rubbers, i.e., impact additives, for use in the process of this invention.

The following table describes the ingredients present in a number of polymerization recipes each of which was polymerized by being introduced into 16 oz. bottles which were then purged with nitrogen for 10 minutes. The bottles were then capped and heated at 70C. for 3 hrs. while being rotated at 20 rpm. The resulting copolymer rubbers were obtained as stable aqueous latices having a resin solids content of about 27-29 perparticle size of about 0.2 0.3 microns.

EXAMPLE VI This example illustrates the preparation of a number of impact resistant PVC compositions which contained, respectively, the various copolymer additives whose preparation is described in Example V, hereinabove. In this instance, the procedure utilized for the preparation of these compositions involved the polymerization of PVC in the presence of an aqueous latex of the previously prepared impact additive copolymer particles. The relationship between the clarity of these compositions and the monomer ratio of the particular impact additive copolymer utilized for their preparation is also shown, the monomer rato being directly determinative of the refractive index of the copolymer. I

The following table describes the ingredients of a number of suspension polymerization recipes each of which was introduced into one quart bottles which were capped and heated at 60C. for a period of 9 hours while being rotated at 37 rpm. In each case, there was produced an aqueous suspension containing about INITIAL COMPOSITION OF POLYMERIZATION RECIPE EMULSIFIER MI 30% BUTYLENE RECIPE COPOLYMER 1% AQUEOUS AQUEOUS BUTYL BENZYL GLYCOL NO. COMPOSITION" H O SOLUTION H 0 SOLUTION DIMETHACRYLATE l 53/45/2 I34 41 3.5 44 37.4 1.65 2 48/50/2 do. do. do. 40 41.5 d0. 3 43/55/2 do. do. do. 35.6 45.5 d0. 4 38/60/2 do. do. do. 31.5 50 do. 5 28/70/2 do. do. do. 23.2 58 do. 6 23/75/2 do. do. do. I) 62 do. 7 Ill/8W2 do. do. do. 15 67 do. 8 l3/85/2 do. do. do. 10.8 70.5 do. 9 40/60 do. do. do. 33 50 None 'I'hc monomer ratio olcach copolymer in the table is 9 wherein no hutylenc glycol dimcthacrylalc is present.

*An anionic surfactant comprising the his(tridecyl) ester of sodium sulfosuccinic acid.

given in the sequence: hulyl acrylatc/hcnzylacrylale/butylene glycol diniclhncrylate except in No.

27 percent, by weight, of particles each of which comprised an intimate, essentially heterogeneous admixture or interpolymer of PVC and about 15 percent, as based on the total weight of each particle, of the particular copolymer additive in whose presence it had been polymerized. In these interpolymer particles, the vinyl chloride had been polymerized in and/or around the particles of the impact additive copolymer. These interpolymer particles were recovered from their respective suspensions on a Buchner funnel and then air dried. In this table, the numbers assigned to the copolymer impact additives correspond to the number by which these additives were identified in the table set forth in Example V. hereinabove.

9 60 Clear 4 60 Clear 5 65 Very Slight haze 6 70 Slight haze 7 75' Some haze 8 80 Some haze The results shown in the above Table indicate that INITIAL COMPOSITION OF POLYMERIZATION RECIPE RECIPE I% SOLUTION AZOBISISO- IMPACT ADDITIVE IMPACT ADDITIVE OF METHYL BUTYRON- VINYL CHLORIDE NO. COPOLYMER LATEX COPOLYMER WATER CELLULOSE ITRILE MONOMER NO." LATEX NO.

I l 58 200 72 0.075 I 2 2 do. do. do. do. 7 do. 3 3 do. do. do. do. do. 4 4 do. do. do. do. do. 5 5 do. do. do. do. do. 6 6 do. do. do. do. do. 7 7 do. do. do. do. dov 8 8 do. do. do. do. do. 9 9 do. do. do. do. do.

The clarity of these interpolymer particles was evaluated by means of a procedure in which 3.0 parts of each respective interpolymer was mixed by hand for about 2-3 minutes with 6.5 parts of dioctyl phthalate and 0.1 parts of an alkyl tin thioglycollate stabilizer as sold by M & T Chemicals, Inc. under the trademark Thermolite 31. A thin layer of each of the resulting plastisol mixtures wasthen spread upon a petri dish. The thus coated dishes were thereupon heated in an oven set at 190C. for a period of about -30 minutes. Upon being removed from the oven, the dried plastisol coatings contained within each dish were visually examined in order to evaluate their clarity. The results of these observations are set forth inthe following table:

PLASTISOL 'YzBENZYL BASED ACRYLATE ON IMPACT IN IMPACT CLARITY OF DRIED ADDITIVE NO, ADDITIVE PLASTISOL COATING I 45 Slight haze 2 50 Very slight haze 3 55 Clear Control Clear PRODUCT BEING TESTED maximum clarity is achieved, with PVC as the substrate, using butyl acrylate: benzylacrylate copolymer additives which contain from about -65 percent, by weight, of benzyl acrylate.

. EXAMPLE VllI This example illustrates the results obtained upon evaluating the impactstrength of the PVC containing the butyl acrylatezbenzyl acrylate copolymer rubber additive incorporated therein; the preparation of the latter product having been described in Example VI hereinabove.

In evaluating these additive copolymers and interpolymer products, they were either milled alone or first diluted with the indicated amount of a commercially available polyvinyl chloride resin. In either case, the milling was conducted on a two-roll mill operating at 350360F. for a period of 3 minutes. As stabilizers, each sample contained 3 PHR of Thermolite 31 and 0.5 PHR of calcium stearate. The following table describes the composition of the various samples which were evaluated as well as the results obtained.

FINAL TENSILE '7 OF 7 PVC" CON C. OF IMPACT PRODUCT USED FOR COPOLYMER STRENGTH USED DILUTION ADDITIVE (Ft/Lbs/ln) Unmodified PVC cannot Impact Additive Copolymer No. 4 of Example V Impact Additive Copolymer No. 4 of Example V PVC having a relative viscosity of 2.II as determined at 30C. in a l gm/deciliter solution of cyclohexanone.

m As determined by means of ASTM Procedure D4822.

The results shown in the above table indicate the improved impact strength inherent in the compositions resulting from the process of this invention when compared with unmodified PVC. It is also to be noted that the products made with the additives of this invention all displayed excellent clarity.

EXAMPLE Vlll This example illustrates the preparation of a, clear, impact resistant composition comprising a blend of a vinyl chloridezvinyl acetate copolymer and one of the novel impact additive copolymers of this invention.

To 100 gms. of an 85:15 vinyl chloridezvinyl acetate copolymer having an intrinsic viscosity of 1.5 as determined in a 1 percent solution of cyclohexanone at 25- C., there was added 37 gms. of the rubber copolymer latex from recipe No. 4 of Example I, hereinabove. The resin-latex mixture was air dried-to remove the water whereupon the resulting product could be formed into PVC sheets having good clarity and impact strength.

EXAMPLE [X In another variation of the process of this invention, it is possible to graft a methyl methacrylate homoor copolymer, i.e., polymethyl methacrylate or a copolymer of methyl methacrylate with a minor proportion of one'or more ethylenically unsaturated comonomers such as ethyl acrylate, onto the previously polymerized particles of one of the above described impact additive rubber copolymers of this invention and to then use the resulting product as an impact additive for PVC or for a rigid copolymer of vinyl chloride. The preparation and use of such a product is illustrated hereinbelow.

The following reactants were placed in a one quart bottle which was capped and heated at 70C. while being rotated for 1 /2 hours at 18 rpm:

268 gms. of the coplymer latex from Recipe No. 5 of Example I hereinabove (75 gms. of rubber) 68 gms. of methyl methacrylate monomer 7 gms. of ethyl acrylate 17 gms. of a 2 percent aqueous solution of 8 0 140 gms. water A latex having a resin solids content of 30 percent, by weight, was obtained which was then air dried so as to obtain a solid polymer product. When this polymer was added to PVC at a 10-20 PHR level it formed a clear blend with improved impact resistance.

Variations may be made in proportions, procedures and materials without departing from the scope of this invention as defined in the following claims.

What is claimed is:

1. An impact additive for use in preparing clear, impact resistant compositions of rigid thermoplastic polymers selected from the group consisting of polyvinyl chloride or a rigid vinyl chloride copolymer substrate, said additive comprising a graft of a methyl methacrylate polymer on a previously prepared copolymer of:

1. at least one C -C alkyl acrylate ester and 2. a second monomer selected from the group consisting of benzyl acrylate and vinylidene chloride, wherein said impact additive copolymer has a monomer ratio of alkyl acrylate ester to benzyl acrylate or vinylidene chloride in the range of from about 35:65 to 55:45.

2. The impact additive of claim 1, wherein said C C alkyl acrylate is butyl acrylate.

3. The impact additive of claim 1, wherein the second monomer of said previously prepared copolymer is benzyl acrylate.

4. The impact additive of claim 1, wherein said'previously prepared copolymer also contains at least one crosslinking comonomer having at least two reactive vinyl groups.

5. The impact additive of claim 4, wherein said crosslinking comonomer is butylene glycol dimethacrylate.

methacrylate with a minor proportion of ethyl acrylate. s

g ga UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,8 1,3 9 Dated June 2 197 Inventor(s) Ruth Gallagher It: is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 57', the term "styrene)," should read --styrene,--

Column 5, line 10, the term "catalst" should read --cata1yst--.

Column 9, line l3,the term "restuls" should read --results-- Column 9, line 64, the term "3. gms. should read --3.6 gms.--

Columns 11 and 12, in the Table, the last three entries are incorrect. The term bu'tyl" should read --butyl acry1ate-'- the term "benzyl" should read --benzyl acrylate--; the terx hutylene glycol" should read --butyl ene'glycol dimethylacrylate-- Column 15 line 38 "coplymer" should read copolymer 3,821,329 Page 2 Cancel the continuity of the Table appearing at the bottom of Column 13 and continuing over to the top of Column 14, and insert the table as shown below:

PLASTISOL BASED ON IMPACT 7JBENZYL ACRYLATE CLARITY OF DRIED ADDITIVE NO. IN IMPACT ADDITIVB PLASTISOL COATING l Slight haze 2 '0 Very slight haze 33 3 l r 2 H Control Clear 9 6o CLear v 4 c1 ear 4 5 i 55 Very slight haze 6 7O Slight haze u a: 7 Some haze a m 8 Some haze 6 163:0 tlii s 15th day of April 1975. 

2. a second monomer selected from the group consisting of benzyl acrylate and vinylidene chloride, wherein said impact additive copolymer has a monomer ratio of alkyl acrylate ester to benzyl acrylate or vinylidene chloride in the range of from about 35: 65 to 55:45.
 2. The impact additive of claim 1, wherein said C1-C12 alkyl acrylate is butyl acrylate.
 3. The impact additive of claim 1, wherein the second monomer of said previously prepared copolymer is benzyl acrylate.
 4. The impact additive of claim 1, wherein said previously prepared copolymer also contains at least one crosslinking comonomer having at least two reactive vinyl groups.
 5. The impact additive of claim 4, wherein said crosslinking comonomer is butylene glycol dimethacrylate.
 6. The impact additive of claim 1, wherein said previously prepared copolymer contains at least one additional non-crosslinking comonomer.
 7. The impact additive of claim 1, wherein said methyl methacrylate polymer is polymethyl methacrylate.
 8. The impact additive of claim 1, wherein said methyl methacrylate polymer is a copolymer of methyl methacrylate with a minor proportion of at least one ethylenically unsaturated comonomer.
 9. The impact additive of claim 8, wherein said methyl methacrylate polymer is a copolymer of methyl methacrylate with a minor proportion of ethyl acrylate. 